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plpgsql_check

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plpgsql_check 2.7.11
Date
Status
Stable
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Abstract
Additional tools for plpgsql functions validation
Description
The plpgsql_check is PostgreSQL extension with functionality for direct or indirect extra validation of functions in plpgsql language. It verifies a validity of SQL identifiers used in plpgsql code. It try to identify a performance issues. Modern versions has integrated profiler. The table and function dependencies can be displayed
Released By
okbob
License
BSD
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Extensions

plpgsql_check 2.7.11
Additional tools for plpgsql functions validation

Documentation

TODO
TODO
custom_scan_function
custom_scan_function

README

Stand With Ukraine

plpgsql_check

This extension is a full linter for plpgsql for PostgreSQL. It leverages only the internal PostgreSQL parser/evaluator so you see exactly the errors would occur at runtime. Furthermore, it parses the SQL inside your routines and finds errors not usually found during the “CREATE PROCEDURE/FUNCTION” command. You can control the levels of many warnings and hints. Finally, you can add PRAGAMA type markers to turn off/on many aspects allowing you to hide messages you already know about, or to remind you to come back for deeper cleaning later.

I founded this project, because I wanted to publish the code I wrote for the two years, when I tried to write enhanced checking for PostgreSQL upstream. It was not fully successful - integration into upstream requires some larger plpgsql refactoring. But the code is fully functional and can be used in production (and it is used in production). So, I created this extension to be available for all plpgsql developers.

If if you want to join our group to help the further development of this extension, register yourself at that postgresql extension hacking google group.

Features

  • checks fields of referenced database objects and types inside embedded SQL
  • validates you are using the correct types for function parameters
  • identifies unused variables and function arguments, unmodified OUT arguments
  • partial detection of dead code (code after an RETURN command)
  • detection of missing RETURN command in function (common after exception handlers, complex logic)
  • tries to identify unwanted hidden casts, which can be a performance issue like unused indexes
  • ability to collect relations and functions used by function
  • ability to check EXECUTE statements against SQL injection vulnerability

I invite any ideas, patches, bugreports.

PostgreSQL PostgreSQL 12 - 17 are supported.

The SQL statements inside PL/pgSQL functions are checked by the validator for semantic errors. These errors can be found by calling the plpgsql_check_function:

Active mode

postgres=# CREATE EXTENSION plpgsql_check;
LOAD
postgres=# CREATE TABLE t1(a int, b int);
CREATE TABLE

postgres=#
CREATE OR REPLACE FUNCTION public.f1()
RETURNS void
LANGUAGE plpgsql
AS $function$
DECLARE r record;
BEGIN
  FOR r IN SELECT * FROM t1
  LOOP
    RAISE NOTICE '%', r.c; -- there is bug - table t1 missing "c" column
  END LOOP;
END;
$function$;

CREATE FUNCTION

postgres=# select f1(); -- execution doesn't find a bug due to empty table t1
  f1 
 ────
   
 (1 row)

postgres=# \x
Expanded display is on.
postgres=# select * from plpgsql_check_function_tb('f1()');
─[ RECORD 1 ]───────────────────────────
functionid │ f1
lineno     │ 6
statement  │ RAISE
sqlstate   │ 42703
message    │ record "r" has no field "c"
detail     │ [null]
hint       │ [null]
level      │ error
position   │ 0
query      │ [null]

postgres=# \sf+ f1
    CREATE OR REPLACE FUNCTION public.f1()
     RETURNS void
     LANGUAGE plpgsql
1       AS $function$
2       DECLARE r record;
3       BEGIN
4         FOR r IN SELECT * FROM t1
5         LOOP
6           RAISE NOTICE '%', r.c; -- there is bug - table t1 missing "c" column
7         END LOOP;
8       END;
9       $function$

Function plpgsql_check_function() has three possible output formats: text, json or xml

select * from plpgsql_check_function('f1()', fatal_errors := false);
                         plpgsql_check_function                         
------------------------------------------------------------------------
 error:42703:4:SQL statement:column "c" of relation "t1" does not exist
 Query: update t1 set c = 30
 --                   ^
 error:42P01:7:RAISE:missing FROM-clause entry for table "r"
 Query: SELECT r.c
 --            ^
 error:42601:7:RAISE:too few parameters specified for RAISE
(7 rows)

postgres=# select * from plpgsql_check_function('fx()', format:='xml');
                 plpgsql_check_function                     
────────────────────────────────────────────────────────────────
 <Function oid="16400">                                        ↵
   <Issue>                                                     ↵
     <Level>error</level>                                      ↵
     <Sqlstate>42P01</Sqlstate>                                ↵
     <Message>relation "foo111" does not exist</Message>       ↵
     <Stmt lineno="3">RETURN</Stmt>                            ↵
     <Query position="23">SELECT (select a from foo111)</Query>↵
   </Issue>                                                    ↵
  </Function>
 (1 row)

Arguments

You can set level of warnings via function’s parameters:

Mandatory argument

  • funcoid oid - function name or function signature - functions require a function specification. Any function in PostgreSQL can be specified by Oid or by name or by signature. When you know oid or complete function’s signature, you can use a regprocedure type parameter like 'fx()'::regprocedure or 16799::regprocedure. Possible alternative is using a name only, when function’s name is unique - like 'fx'. When the name is not unique or the function doesn’t exists it raises a error.

Optional arguments

  • relid DEFAULT 0 - oid of relation assigned with trigger function. It is necessary to check any trigger function. You are sending the table in that the trigger operates on.

  • fatal_errors boolean DEFAULT true - stop on first error (prevents massive error reports)

  • other_warnings boolean DEFAULT true - show warnings like different attributes number in assignmenet on left and right side, variable overlaps function’s parameter, unused variables, unwanted casting, etc.

  • extra_warnings boolean DEFAULT true - show warnings like missing RETURN, shadowed variables, dead code, never read (unused) function’s parameter, unmodified variables, modified auto variables, etc.

  • performance_warnings boolean DEFAULT false - performance related warnings like declared type with type modifier, casting, implicit casts in where clause (can be the reason why an index is not used), etc.

  • security_warnings boolean DEFAULT false - security related checks like SQL injection vulnerability detection

  • compatibility_warnings boolean DEFAULT false - compatibility related checks like obsolete explicit setting internal cursor names in refcursor’s or cursor’s variables.

  • anyelementtype regtype DEFAULT 'int' - an actual type to be used when testing the anyelement type

  • anyenumtype regtype DEFAULT '-' - an actual type to be used when testing the anyenum type

  • anyrangetype regtype DEFAULT 'int4range' - an actual type to be used when testing the anyrange type

  • anycompatibletype DEFAULT 'int' - an actual type to be used when testing the anycompatible type

  • anycompatiblerangetype DEFAULT 'int4range' - an actual range type to be used when testing the anycompatible range type

  • without_warnings DEFAULT false - disable all warnings (Ignores all xxxx_warning parameters, a quick override)

  • all_warnings DEFAULT false - enable all warnings (Ignores other xxx_warning parameters, a quick positive)

  • newtable DEFAULT NULL, oldtable DEFAULT NULL - the names of NEW or OLD transition tables. These parameters are required when transition tables are used in trigger functions.

  • use_incomment_options DEFAULT true - when it is true, then in-comment options are active

  • incomment_options_usage_warning DEFAULT false - when it is true, then the warning is raised when in-comment option is used.

  • constant_tracing boolean DEFAULT true - when it is true, then the variable that holds some constant content, can be used like constant (it is work only in some simple cases, and the content of variable should not be ambigonuous).

Triggers

When you want to check any trigger, you have to enter a relation that will be used together with trigger function

CREATE TABLE bar(a int, b int);

postgres=# \sf+ foo_trg
    CREATE OR REPLACE FUNCTION public.foo_trg()
         RETURNS trigger
         LANGUAGE plpgsql
1       AS $function$
2       BEGIN
3         NEW.c := NEW.a + NEW.b;
4         RETURN NEW;
5       END;
6       $function$

Missing relation specification

postgres=# select * from plpgsql_check_function('foo_trg()');
ERROR:  missing trigger relation
HINT:  Trigger relation oid must be valid

Correct trigger checking (with specified relation)

postgres=# select * from plpgsql_check_function('foo_trg()', 'bar');
                 plpgsql_check_function                 
--------------------------------------------------------
 error:42703:3:assignment:record "new" has no field "c"
(1 row)

For triggers with transitive tables you can set the oldtable and newtable parameters:

create or replace function footab_trig_func()
returns trigger as $$
declare x int;
begin
  if false then
    -- should be ok;
    select count(*) from newtab into x; 

    -- should fail;
    select count(*) from newtab where d = 10 into x;
  end if;
  return null;
end;
$$ language plpgsql;

select * from plpgsql_check_function('footab_trig_func','footab', newtable := 'newtab');

In-comment options

plpgsql_check allows persistent setting written in comments. These options are taken from function’s source code before checking. The syntax is:

@plpgsql_check_option: optioname [=] value [, optname [=] value ...]

The settings from comment options has top high priority, but generally it can be disabled by option use_incomment_options to false.

Example:

create or replace function fx(anyelement)
returns text as $$
begin
  /*
   * rewrite default polymorphic type to text
   * @plpgsql_check_options: anyelementtype = text
   */
  return $1;
end;
$$ language plpgsql;

Checking all of your code

You can use the plpgsql_check_function for mass checking of functions/procedures and mass checking of triggers. Please, test following queries:

-- check all nontrigger plpgsql functions
SELECT p.oid, p.proname, plpgsql_check_function(p.oid)
   FROM pg_catalog.pg_namespace n
   JOIN pg_catalog.pg_proc p ON pronamespace = n.oid
   JOIN pg_catalog.pg_language l ON p.prolang = l.oid
  WHERE l.lanname = 'plpgsql' AND p.prorettype <> 2279;

or

-- check all trigger plpgsql functions
SELECT p.proname, tgrelid::regclass, cf.*
   FROM pg_proc p
        JOIN pg_trigger t ON t.tgfoid = p.oid 
        JOIN pg_language l ON p.prolang = l.oid
        JOIN pg_namespace n ON p.pronamespace = n.oid,
        LATERAL plpgsql_check_function(p.oid, t.tgrelid) cf
  WHERE n.nspname = 'public' and l.lanname = 'plpgsql';

or

-- check all plpgsql functions (functions or trigger functions with defined triggers)
SELECT
    (pcf).functionid::regprocedure, (pcf).lineno, (pcf).statement,
    (pcf).sqlstate, (pcf).message, (pcf).detail, (pcf).hint, (pcf).level,
    (pcf)."position", (pcf).query, (pcf).context
FROM
(
    SELECT
        plpgsql_check_function_tb(pg_proc.oid, COALESCE(pg_trigger.tgrelid, 0)) AS pcf
    FROM pg_proc
    LEFT JOIN pg_trigger
        ON (pg_trigger.tgfoid = pg_proc.oid)
    WHERE
        prolang = (SELECT lang.oid FROM pg_language lang WHERE lang.lanname = 'plpgsql') AND
        pronamespace <> (SELECT nsp.oid FROM pg_namespace nsp WHERE nsp.nspname = 'pg_catalog') AND
        -- ignore unused triggers
        (pg_proc.prorettype <> (SELECT typ.oid FROM pg_type typ WHERE typ.typname = 'trigger') OR
         pg_trigger.tgfoid IS NOT NULL)
    OFFSET 0
) ss
ORDER BY (pcf).functionid::regprocedure::text, (pcf).lineno;

Passive mode (only recommended for development or preproduction)

Functions can be checked upon execution - plpgsql_check module must be loaded (via postgresql.conf).

Configuration Settings

plpgsql_check.mode = [ disabled | by_function | fresh_start | every_start ]
plpgsql_check.fatal_errors = [ yes | no ]

plpgsql_check.show_nonperformance_warnings = false
plpgsql_check.show_performance_warnings = false

Default mode is by_function, that means that the enhanced check is done only in active mode - by calling the plpgsql_check_function. fresh_start means cold start (first the function is called).

You can enable passive mode by

load 'plpgsql'; -- 1.1 and higher doesn't need it
load 'plpgsql_check';
set plpgsql_check.mode = 'every_start';  -- This scans all code before it is executed

SELECT fx(10); -- run functions - function is checked before runtime starts it

Compatibility warnings

Assigning string to refcursor variable

PostgreSQL cursor’s and refcursor’s variables are enhanced string variables that holds unique name of related portal (internal structure of Postgres that is used for cursor’s implementation). Until PostgreSQL 16, the the portal had same name like name of cursor variable. PostgreSQL 16 and higher change this mechanism and by default related portal will be named by some unique name. It solves some issues with cursors in nested blocks or when cursor is used in recursive called function.

With mentioned change, the refcursor’s variable should to take value from another refcursor variable or from some cursor variable (when cursor is opened).

-- obsolete pattern
DECLARE
  cur CURSOR FOR SELECT 1;
  rcur refcursor;
BEGIN
  rcur := 'cur';
  OPEN cur;
  ...

-- new pattern
DECLARE
  cur CURSOR FOR SELECT 1;
  rcur refcursor;
BEGIN
  OPEN cur;
  rcur := cur;
  ...

When compatibility_warnings flag is active, then plpgsql_check try to identify some fishy assigning to refcursor’s variable or returning of refcursor’s values:

CREATE OR REPLACE FUNCTION public.foo()
 RETURNS refcursor
AS $$
declare
   c cursor for select 1;
   r refcursor;
begin
  open c;
  r := 'c';
  return r;
end;
$$ LANGUAGE plpgsql;

select * from plpgsql_check_function('foo', extra_warnings =>false, compatibility_warnings => true);
┌───────────────────────────────────────────────────────────────────────────────────┐
│                              plpgsql_check_function                               │
╞═══════════════════════════════════════════════════════════════════════════════════╡
│ compatibility:00000:6:assignment:obsolete setting of refcursor or cursor variable │
│ Detail: Internal name of cursor should not be specified by users.                 │
│ Context: at assignment to variable "r" declared on line 3                         │
└───────────────────────────────────────────────────────────────────────────────────┘
(3 rows)

Limits

plpgsql_check should find almost all errors on really static code. When developers use PLpgSQL’s dynamic features like dynamic SQL or record data type, then false positives are possible. These should be rare - in well written code - and then the affected function should be redesigned or plpgsql_check should be disabled for this function.

CREATE OR REPLACE FUNCTION f1()
RETURNS void AS $$
DECLARE r record;
BEGIN
  FOR r IN EXECUTE 'SELECT * FROM t1'
  LOOP
    RAISE NOTICE '%', r.c;
  END LOOP;
END;
$$ LANGUAGE plpgsql SET plpgsql.enable_check TO false;

A usage of plpgsql_check adds a small overhead (when passive mode is enabled) and you should use that setting only in development or preproduction environments.

Dynamic SQL

This module doesn’t check queries that are assembled in runtime. It is not possible to identify results of dynamic queries - so plpgsql_check cannot to set correct type to record variables and cannot to check a dependent SQLs and expressions.

When type of record’s variable is not know, you can assign it explicitly with pragma type:

DECLARE r record;
BEGIN
  EXECUTE format('SELECT * FROM %I', _tablename) INTO r;
  PERFORM plpgsql_check_pragma('type: r (id int, processed bool)');
  IF NOT r.processed THEN
    ...

Refcursors

plpgsql_check cannot be used to detect structure of referenced cursors. A reference on cursor in PLpgSQL is implemented as name of global cursor. In check time, the name is not known (not in all possibilities), and global cursor doesn’t exist. It is a significant issue for any static analysis. PLpgSQL cannot know how to set the correct type for the record variables and cannot to check the dependent SQL statements and expressions. A solution is the same for dynamic SQL. Don’t use record variable as target when you use refcursor type or disable plpgsql_check for these functions.

CREATE OR REPLACE FUNCTION foo(refcur_var refcursor)
RETURNS void AS $$
DECLARE
  rec_var record;
BEGIN
  FETCH refcur_var INTO rec_var; -- this is STOP for plpgsql_check
  RAISE NOTICE '%', rec_var;     -- record rec_var is not assigned yet error

In this case a record type should not be used (use known rowtype instead):

CREATE OR REPLACE FUNCTION foo(refcur_var refcursor)
RETURNS void AS $$
DECLARE
  rec_var some_rowtype;
BEGIN
  FETCH refcur_var INTO rec_var;
  RAISE NOTICE '%', rec_var;

Temporary tables

plpgsql_check cannot verify queries over temporary tables that are created in plpgsql’s function runtime. For this use case it is necessary to create a fake temp table or disable plpgsql_check for this function.

In reality temp tables are stored in own (per user) schema with higher priority than persistent tables. So you can do (with following trick safetly):

CREATE OR REPLACE FUNCTION public.disable_dml()
RETURNS trigger
LANGUAGE plpgsql AS $function$
BEGIN
  RAISE EXCEPTION SQLSTATE '42P01'
     USING message = format('this instance of %I table doesn''t allow any DML operation', TG_TABLE_NAME),
           hint = format('you should use "CREATE TEMP TABLE %1$I(LIKE %1$I INCLUDING ALL);" statement',
                         TG_TABLE_NAME);
  RETURN NULL;
END;
$function$;

CREATE TABLE foo(a int, b int); -- doesn't hold data, ever
CREATE TRIGGER foo_disable_dml
   BEFORE INSERT OR UPDATE OR DELETE ON foo
   EXECUTE PROCEDURE disable_dml();

postgres=# INSERT INTO  foo VALUES(10,20);
ERROR:  this instance of foo table doesn't allow any DML operation
HINT:  you should to run "CREATE TEMP TABLE foo(LIKE foo INCLUDING ALL);" statement
postgres=# 

CREATE TABLE
postgres=# INSERT INTO  foo VALUES(10,20);
INSERT 0 1

This trick emulates GLOBAL TEMP tables partially and it allows a statical validation. Other possibility is using a [template foreign data wrapper] (https://github.com/okbob/template_fdw)

You can use pragma table and create ephemeral table:

BEGIN
   CREATE TEMP TABLE xxx(a int);
   PERFORM plpgsql_check_pragma('table: xxx(a int)');
   INSERT INTO xxx VALUES(10);
   PERFORM plpgsql_check_pragma('table: [pg_temp].zzz(like schemaname.table1 including all)');
   ...

Dependency list

A function plpgsql_show_dependency_tb will show all functions, operators and relations used inside processed function:

postgres=# select * from plpgsql_show_dependency_tb('testfunc(int,float)');
┌──────────┬───────┬────────┬─────────┬────────────────────────────┐
│   type   │  oid  │ schema │  name   │           params           │
╞══════════╪═══════╪════════╪═════════╪════════════════════════════╡
│ FUNCTION │ 36008 │ public │ myfunc1 │ (integer,double precision) │
│ FUNCTION │ 35999 │ public │ myfunc2 │ (integer,double precision) │
│ OPERATOR │ 36007 │ public │ **      │ (integer,integer)          │
│ RELATION │ 36005 │ public │ myview  │                            │
│ RELATION │ 36002 │ public │ mytable │                            │
└──────────┴───────┴────────┴─────────┴────────────────────────────┘
(4 rows)

Optional arguments of plpgsql_show_dependency_tb are relid, anyelementtype, enumtype, anyrangetype, anycompatibletype and anycompatiblerangetype.

Profiler

The plpgsql_check contains simple profiler of plpgsql functions and procedures. It can work with/without access to shared memory. It depends on shared_preload_libraries config. When plpgsql_check is initialized by shared_preload_libraries, then it can allocate shared memory, and function’s profiles are stored there. When plpgsql_check cannot to allocate shared memory, the profile is stored in session memory.

Due to dependencies, shared_preload_libraries should to contain plpgsql first

postgres=# show shared_preload_libraries ;
┌──────────────────────────┐
│ shared_preload_libraries │
╞══════════════════════════╡
│ plpgsql,plpgsql_check    │
└──────────────────────────┘
(1 row)

The profiler is active when GUC plpgsql_check.profiler is on. The profiler doesn’t require shared memory, but if there is not enough shared memory, then the profiler is limited just to active session. The profiler can be activated by calling function plpgsql_check_profiler(true) and disabled by calling same function with false argument (or with literals on, off).

The plpgsql_check should be initialized before any plpgsql function is executed. Only early initialization ensures correct work of profiler and tracer. When you doesn’t use shared_preloaded_libraries, you can use command load 'plpgsql_check' instead.

When plpgsql_check is initialized by shared_preload_libraries, another GUC is available to configure the amount of shared memory used by the profiler: plpgsql_check.profiler_max_shared_chunks. This defines the maximum number of statements chunk that can be stored in shared memory. For each plpgsql function (or procedure), the whole content is split into chunks of 30 statements. If needed, multiple chunks can be used to store the whole content of a single function. A single chunk is 1704 bytes. The default value for this GUC is 15000, which should be enough for big projects containing hundreds of thousands of statements in plpgsql, and will consume about 24MB of memory. If your project doesn’t require that much number of chunks, you can set this parameter to a smaller number in order to decrease the memory usage. The minimum value is 50 (which should consume about 83kB of memory), and the maximum value is 100000 (which should consume about 163MB of memory). Changing this parameter requires a PostgreSQL restart.

The profiler will also retrieve the query identifier for each instruction that contains an expression or optimizable statement. Note that this requires pg_stat_statements, or another similar third-party extension), to be installed. There are some limitations to the query identifier retrieval:

  • if a plpgsql expression contains underlying statements, only the top level query identifier will be retrieved
  • the profiler doesn’t compute query identifier by itself but relies on external extension, such as pg_stat_statements, for that. It means that depending on the external extension behavior, you may not be able to see a query identifier for some statements. That’s for instance the case with DDL statements, as pg_stat_statements doesn’t expose the query identifier for such queries.
  • a query identifier is retrieved only for instructions containing expressions. This means that plpgsql_profiler_function_tb() function can report less query identifier than instructions on a single line.

Attention: An update of shared profiles can decrease performance on servers under higher load.

The profile can be displayed by function plpgsql_profiler_function_tb:

postgres=# select lineno, avg_time, source from plpgsql_profiler_function_tb('fx(int)');
┌────────┬──────────┬───────────────────────────────────────────────────────────────────┐
│ lineno │ avg_time │                              source                               │
╞════════╪══════════╪═══════════════════════════════════════════════════════════════════╡
│      1 │          │                                                                   │
│      2 │          │ declare result int = 0;                                           │
│      3 │    0.075 │ begin                                                             │
│      4 │    0.202 │   for i in 1..$1 loop                                             │
│      5 │    0.005 │     select result + i into result; select result + i into result; │
│      6 │          │   end loop;                                                       │
│      7 │        0 │   return result;                                                  │
│      8 │          │ end;                                                              │
└────────┴──────────┴───────────────────────────────────────────────────────────────────┘
(9 rows)

The times in the result are in miliseconds.

The profile per statements (not per line) can be displayed by function plpgsql_profiler_function_statements_tb:

        CREATE OR REPLACE FUNCTION public.fx1(a integer)
         RETURNS integer
         LANGUAGE plpgsql
1       AS $function$
2       begin
3         if a > 10 then
4           raise notice 'ahoj';
5           return -1;
6         else
7           raise notice 'nazdar';
8           return 1;
9         end if;
10      end;
11      $function$

postgres=# select stmtid, parent_stmtid, parent_note, lineno, exec_stmts, stmtname
             from plpgsql_profiler_function_statements_tb('fx1');
┌────────┬───────────────┬─────────────┬────────┬────────────┬─────────────────┐
│ stmtid │ parent_stmtid │ parent_note │ lineno │ exec_stmts │    stmtname     │
╞════════╪═══════════════╪═════════════╪════════╪════════════╪═════════════════╡
│      0 │             ∅ │ ∅           │      2 │          0 │ statement block │
│      1 │             0 │ body        │      3 │          0 │ IF              │
│      2 │             1 │ then body   │      4 │          0 │ RAISE           │
│      3 │             1 │ then body   │      5 │          0 │ RETURN          │
│      4 │             1 │ else body   │      7 │          0 │ RAISE           │
│      5 │             1 │ else body   │      8 │          0 │ RETURN          │
└────────┴───────────────┴─────────────┴────────┴────────────┴─────────────────┘
(6 rows)

All stored profiles can be displayed by calling function plpgsql_profiler_functions_all:

postgres=# select * from plpgsql_profiler_functions_all();
┌───────────────────────┬────────────┬────────────┬──────────┬─────────────┬──────────┬──────────┐
│        funcoid        │ exec_count │ total_time │ avg_time │ stddev_time │ min_time │ max_time │
╞═══════════════════════╪════════════╪════════════╪══════════╪═════════════╪══════════╪══════════╡
│ fxx(double precision) │          1 │       0.01 │     0.01 │        0.00 │     0.01 │     0.01 │
└───────────────────────┴────────────┴────────────┴──────────┴─────────────┴──────────┴──────────┘
(1 row)

There are two functions for cleaning stored profiles: plpgsql_profiler_reset_all() and plpgsql_profiler_reset(regprocedure).

Coverage metrics

plpgsql_check provides two functions:

  • plpgsql_coverage_statements(name)
  • plpgsql_coverage_branches(name)

Note

There is another very good PLpgSQL profiler - https://github.com/glynastill/plprofiler

My extension is designed to be simple for use and practical. Nothing more or less.

plprofiler is more complex. It builds call graphs and from this graph it can create flame graph of execution times.

Both extensions can be used together with the builtin PostgreSQL’s feature - tracking functions.

set track_functions to 'pl';
...
select * from pg_stat_user_functions;

Tracer

plpgsql_check provides a tracing possibility - in this mode you can see notices on start or end functions (terse and default verbosity) and start or end statements (verbose verbosity). For default and verbose verbosity the content of function arguments is displayed. The content of related variables are displayed when verbosity is verbose.

postgres=# do $$ begin perform fx(10,null, 'now', e'stěhule'); end; $$;
NOTICE:  #0 ->> start of inline_code_block (Oid=0)
NOTICE:  #2   ->> start of function fx(integer,integer,date,text) (Oid=16405)
NOTICE:  #2        call by inline_code_block line 1 at PERFORM
NOTICE:  #2       "a" => '10', "b" => null, "c" => '2020-08-03', "d" => 'stěhule'
NOTICE:  #4     ->> start of function fx(integer) (Oid=16404)
NOTICE:  #4          call by fx(integer,integer,date,text) line 1 at PERFORM
NOTICE:  #4         "a" => '10'
NOTICE:  #4     <<- end of function fx (elapsed time=0.098 ms)
NOTICE:  #2   <<- end of function fx (elapsed time=0.399 ms)
NOTICE:  #0 <<- end of block (elapsed time=0.754 ms)

The number after # is a execution frame counter (this number is related to depth of error context stack). It allows to pair start and end of function.

Tracing is enabled by setting plpgsql_check.tracer to on. Attention - enabling this behaviour has significant negative impact on performance (unlike the profiler). You can set a level for output used by tracer plpgsql_check.tracer_errlevel (default is notice). The output content is limited by length specified by plpgsql_check.tracer_variable_max_length configuration variable. The tracer can be activated by calling function plpgsql_check_tracer(true) and disabled by calling same function with false argument (or with literals on, off).

First, the usage of tracer should be explicitly enabled by superuser by setting set plpgsql_check.enable_tracer to on; or plpgsql_check.enable_tracer to on in postgresql.conf. This is a security safeguard. The tracer shows content of plpgsql’s variables, and then some security sensitive information can be displayed to an unprivileged user (when he runs security definer function). Second, the extension plpgsql_check should be loaded. It can be done by execution of some plpgsql_check function or explicitly by command load 'plpgsql_check';. You can use configuration’s option shared_preload_libraries, local_preload_libraries or session_preload_libraries.

In terse verbose mode the output is reduced:

postgres=# set plpgsql_check.tracer_verbosity TO terse;
SET
postgres=# do $$ begin perform fx(10,null, 'now', e'stěhule'); end; $$;
NOTICE:  #0 start of inline code block (oid=0)
NOTICE:  #2 start of fx (oid=16405)
NOTICE:  #4 start of fx (oid=16404)
NOTICE:  #4 end of fx
NOTICE:  #2 end of fx
NOTICE:  #0 end of inline code block

In verbose mode the output is extended about statement details:

postgres=# do $$ begin perform fx(10,null, 'now', e'stěhule'); end; $$;
NOTICE:  #0            ->> start of block inline_code_block (oid=0)
NOTICE:  #0.1       1  --> start of PERFORM
NOTICE:  #2              ->> start of function fx(integer,integer,date,text) (oid=16405)
NOTICE:  #2                   call by inline_code_block line 1 at PERFORM
NOTICE:  #2                  "a" => '10', "b" => null, "c" => '2020-08-04', "d" => 'stěhule'
NOTICE:  #2.1       1    --> start of PERFORM
NOTICE:  #2.1                "a" => '10'
NOTICE:  #4                ->> start of function fx(integer) (oid=16404)
NOTICE:  #4                     call by fx(integer,integer,date,text) line 1 at PERFORM
NOTICE:  #4                    "a" => '10'
NOTICE:  #4.1       6      --> start of assignment
NOTICE:  #4.1                  "a" => '10', "b" => '20'
NOTICE:  #4.1              <-- end of assignment (elapsed time=0.076 ms)
NOTICE:  #4.1                  "res" => '130'
NOTICE:  #4.2       7      --> start of RETURN
NOTICE:  #4.2                  "res" => '130'
NOTICE:  #4.2              <-- end of RETURN (elapsed time=0.054 ms)
NOTICE:  #4                <<- end of function fx (elapsed time=0.373 ms)
NOTICE:  #2.1            <-- end of PERFORM (elapsed time=0.589 ms)
NOTICE:  #2              <<- end of function fx (elapsed time=0.727 ms)
NOTICE:  #0.1          <-- end of PERFORM (elapsed time=1.147 ms)
NOTICE:  #0            <<- end of block (elapsed time=1.286 ms)

A special feature of tracer is tracing of the ASSERT statement when plpgsql_check.trace_assert is on. When plpgsql_check.trace_assert_verbosity is DEFAULT, then all function’s or procedure’s variables are displayed when assert expression is false. When this configuration is VERBOSE then all variables from all plpgsql frames are displayed. This behaviour is independent on plpgsql.check_asserts value. It can be used, although the assertions are disabled in plpgsql runtime.

postgres=# set plpgsql_check.tracer to off;
postgres=# set plpgsql_check.trace_assert_verbosity TO verbose;

postgres=# do $$ begin perform fx(10,null, 'now', e'stěhule'); end; $$;
NOTICE:  #4 PLpgSQL assert expression (false) on line 12 of fx(integer) is false
NOTICE:   "a" => '10', "res" => null, "b" => '20'
NOTICE:  #2 PL/pgSQL function fx(integer,integer,date,text) line 1 at PERFORM
NOTICE:   "a" => '10', "b" => null, "c" => '2020-08-05', "d" => 'stěhule'
NOTICE:  #0 PL/pgSQL function inline_code_block line 1 at PERFORM
ERROR:  assertion failed
CONTEXT:  PL/pgSQL function fx(integer) line 12 at ASSERT
SQL statement "SELECT fx(a)"
PL/pgSQL function fx(integer,integer,date,text) line 1 at PERFORM
SQL statement "SELECT fx(10,null, 'now', e'stěhule')"
PL/pgSQL function inline_code_block line 1 at PERFORM

postgres=# set plpgsql.check_asserts to off;
SET
postgres=# do $$ begin perform fx(10,null, 'now', e'stěhule'); end; $$;
NOTICE:  #4 PLpgSQL assert expression (false) on line 12 of fx(integer) is false
NOTICE:   "a" => '10', "res" => null, "b" => '20'
NOTICE:  #2 PL/pgSQL function fx(integer,integer,date,text) line 1 at PERFORM
NOTICE:   "a" => '10', "b" => null, "c" => '2020-08-05', "d" => 'stěhule'
NOTICE:  #0 PL/pgSQL function inline_code_block line 1 at PERFORM
DO

Tracer can show usage of subtransaction buffer id (nxids). The displayed tnl number is transaction nesting level number (for plpgsql it depends on deep of blocks with exception’s handlers).

Detection of unclosed cursors

PLpgSQL’s cursors are just names of SQL cursors. The life cycle of SQL cursors is not joined with scope of related plpgsql’s cursor variable. SQL cursors are cloased by self at transaction end, but for long transaction and too much opened cursors it can be too late. It is better to close cursor explicitly when cursor is not necessary (by CLOSE statement). Without it the significant memory issues are possible.

When OPEN statement try to use cursor that is not closed yet, the warning is raised. This feature can be disabled by setting plpgsql_check.cursors_leaks to off. This check is not active, when routine is called recusively

The unclosed cursors can be checked immediately when function is finished. This check is disabled by default, and should be enabled by plpgsql_check.strict_cursors_leaks to on.

Any unclosed cursor is reported once.

Using with plugin_debugger

If you use plugin_debugger (plpgsql debugger) together with plpgsql_check, then plpgsql_check should be initialized after plugin_debugger (because plugin_debugger doesn’t support the sharing of PL/pgSQL’s debug API). For example (postgresql.conf):

shared_preload_libraries = 'plugin_debugger,plpgsql,plpgsql_check'

Attention - SECURITY

Tracer prints content of variables or function arguments. For security definer function, this content can hold security sensitive data. This is reason why tracer is disabled by default and should be enabled only with super user rights plpgsql_check.enable_tracer.

Pragma

You can configure plpgsql_check behaviour inside a checked function with “pragma” function. This is a analogy of PL/SQL or ADA language of PRAGMA feature. PLpgSQL doesn’t support PRAGMA, but plpgsql_check detects function named plpgsql_check_pragma and takes options from the parameters of this function. These plpgsql_check options are valid to the end of this group of statements.

CREATE OR REPLACE FUNCTION test()
RETURNS void AS $$
BEGIN
  ...
  -- for following statements disable check
  PERFORM plpgsql_check_pragma('disable:check');
  ...
  -- enable check again
  PERFORM plpgsql_check_pragma('enable:check');
  ...
END;
$$ LANGUAGE plpgsql;

The function plpgsql_check_pragma is immutable function that returns one. It is defined by plpgsql_check extension. You can declare alternative plpgsql_check_pragma function like:

CREATE OR REPLACE FUNCTION plpgsql_check_pragma(VARIADIC args[])
RETURNS int AS $$
SELECT 1
$$ LANGUAGE sql IMMUTABLE;

Using pragma function in declaration part of top block sets options on function level too.

CREATE OR REPLACE FUNCTION test()
RETURNS void AS $$
DECLARE
  aux int := plpgsql_check_pragma('disable:extra_warnings');
  ...

Shorter syntax for pragma is supported too:

CREATE OR REPLACE FUNCTION test()
RETURNS void AS $$
DECLARE r record;
BEGIN
  PERFORM 'PRAGMA:TYPE:r (a int, b int)';
  PERFORM 'PRAGMA:TABLE: x (like pg_class)';
  ...

Supported pragmas

  • echo:str - print string (for testing). Inside string, there can be used “variables”: @@id, @@name, @@signature

  • status:check,status:tracer, status:other_warnings, status:performance_warnings, status:extra_warnings,status:security_warnings This outputs the current value (e.g. other_warnings enabled)

  • enable:check,enable:tracer, enable:other_warnings, enable:performance_warnings, enable:extra_warnings,enable:security_warnings

  • disable:check,disable:tracer, disable:other_warnings, disable:performance_warnings, disable:extra_warnings,disable:security_warnings This can be used to disable the Hint in returning from an anyelement function. Just put the pragma before the RETURN statement.

  • type:varname typename or type:varname (fieldname type, ...) - set type to variable of record type

  • table: name (column_name type, ...) or table: name (like tablename) - create ephemeral temporary table (if you want to specify schema, then only pg_temp schema is allowed.

  • sequence: name - create ephemeral temporary sequence

  • assert-schema: varname - check-time assertation - ensure so schema specified by variable is valid

  • assert-table: [ varname_schema, ] , varname - ensure so table name specified by variables (by constant tracing) is valid

  • assert-column: [varname_schema, ], varname_table , varname - ensure so column spefified by variables is valid

Pragmas enable:tracer and disable:tracerare active for Postgres 12 and higher

Update

plpgsql_check doesn’t support update (of plpgsql_check). You should to drop this before install new version of this extension.

Compilation

You need a development environment for PostgreSQL extensions:

make clean
make install

result:

[pavel@localhost plpgsql_check]$ make USE_PGXS=1 clean
rm -f plpgsql_check.so   libplpgsql_check.a  libplpgsql_check.pc
rm -f plpgsql_check.o
rm -rf results/ regression.diffs regression.out tmp_check/ log/
[pavel@localhost plpgsql_check]$ make USE_PGXS=1 all
clang -O2 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fpic -I/usr/local/pgsql/lib/pgxs/src/makefiles/../../src/pl/plpgsql/src -I. -I./ -I/usr/local/pgsql/include/server -I/usr/local/pgsql/include/internal -D_GNU_SOURCE   -c -o plpgsql_check.o plpgsql_check.c
clang -O2 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fpic -I/usr/local/pgsql/lib/pgxs/src/makefiles/../../src/pl/plpgsql/src -shared -o plpgsql_check.so plpgsql_check.o -L/usr/local/pgsql/lib -Wl,--as-needed -Wl,-rpath,'/usr/local/pgsql/lib',--enable-new-dtags  
[pavel@localhost plpgsql_check]$ su root
Password: *******
[root@localhost plpgsql_check]# make USE_PGXS=1 install
/usr/bin/mkdir -p '/usr/local/pgsql/lib'
/usr/bin/mkdir -p '/usr/local/pgsql/share/extension'
/usr/bin/mkdir -p '/usr/local/pgsql/share/extension'
/usr/bin/install -c -m 755  plpgsql_check.so '/usr/local/pgsql/lib/plpgsql_check.so'
/usr/bin/install -c -m 644 plpgsql_check.control '/usr/local/pgsql/share/extension/'
/usr/bin/install -c -m 644 plpgsql_check--0.9.sql '/usr/local/pgsql/share/extension/'
[root@localhost plpgsql_check]# exit
[pavel@localhost plpgsql_check]$ make USE_PGXS=1 installcheck
/usr/local/pgsql/lib/pgxs/src/makefiles/../../src/test/regress/pg_regress --inputdir=./ --psqldir='/usr/local/pgsql/bin'    --dbname=pl_regression --load-language=plpgsql --dbname=contrib_regression plpgsql_check_passive plpgsql_check_active plpgsql_check_active-9.5
(using postmaster on Unix socket, default port)
============== dropping database "contrib_regression" ==============
DROP DATABASE
============== creating database "contrib_regression" ==============
CREATE DATABASE
ALTER DATABASE
============== installing plpgsql                     ==============
CREATE LANGUAGE
============== running regression test queries        ==============
test plpgsql_check_passive    ... ok
test plpgsql_check_active     ... ok
test plpgsql_check_active-9.5 ... ok

=====================
 All 3 tests passed. 
=====================

Compilation on Ubuntu

Sometimes successful compilation can require libicu-dev package (PostgreSQL 10 and higher - when pg was compiled with ICU support)

sudo apt install libicu-dev

Compilation plpgsql_check on Windows

You can check precompiled dll libraries http://okbob.blogspot.cz/2015/02/plpgsqlcheck-is-available-for-microsoft.html, http://okbob.blogspot.com/2023/10/compiled-dll-of-plpgsqlcheck-254-and.html

or compile by self:

  1. Download and install PostgreSQL for Win32 from http://www.enterprisedb.com
  2. Download and install Microsoft Visual C++ Express
  3. Read tutorial http://blog.2ndquadrant.com/compiling-postgresql-extensions-visual-studio-windows
  4. Build plpgsql_check.dll
  5. Install plugin
  6. copy plpgsql_check.dll to PostgreSQL\14\lib
  7. copy plpgsql_check.control and plpgsql_check--2.1.sql to PostgreSQL\14\share\extension

Checked on

  • gcc on Linux (against all supported PostgreSQL)
  • clang 3.4 on Linux (against PostgreSQL 10)
  • for success regress tests the PostgreSQL 10 or higher is required

Compilation against PostgreSQL 10 requires libICU!

Licence

Copyright (c) Pavel Stehule (pavel.stehule@gmail.com)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Note

If you like it, send a postcard to address

Pavel Stehule
Skalice 12
256 01 Benesov u Prahy
Czech Republic

I invite any questions, comments, bug reports, patches on mail address pavel.stehule@gmail.com